Safe Blender Download Mirrors
Windows:
https://mirror.clarkson.edu/blender/release/Blender2.81/blender-2.81a-windows64.msi

Windows - Portable (.zip): https://mirror.clarkson.edu/blender/release/Blender2.81/blender-2.81a-windows64.zip

macOS:
https://mirror.clarkson.edu/blender/release/Blender2.81/blender-2.81a-macOS.dmg

Linux:
https://mirror.clarkson.edu/blender/release/Blender2.81/blender-2.81a-linux-glibc217-x86_64.tar.bz2

I got these links using the tool Wayback Machine (https://web.archive.org/). It has a saved Blender download page from few days ago (https://web.archive.org/web/20200125185852/https://www.blender.org/download/). When you click on download it appears to you a "thank you" page, then there is a link on a text on the bottom of that page ("Your download should begin automatically. If it doesn't, click here to retry."), which leads to an official mirror download. You click on it and the download will start.